Mercurial > hg > index.cgi
diff docs/manual/x534.html @ 324:b30091890d62
Add documentation of the new hex output formats.
Thanks to text contributed by Tom LeMense, the manual now includes
documentation of the hex formats he contributed. This also includes some
updated text on the ORG directive. Only minor editorial changes vary the
text from Tom's original.
| author | William Astle <lost@l-w.ca> |
|---|---|
| date | Tue, 04 Mar 2014 23:10:13 -0700 |
| parents | |
| children |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/docs/manual/x534.html Tue Mar 04 23:10:13 2014 -0700 @@ -0,0 +1,228 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"> +<HTML +><HEAD +><TITLE +>Structures</TITLE +><META +NAME="GENERATOR" +CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK +REL="HOME" +TITLE="LW Tool Chain" +HREF="index.html"><LINK +REL="UP" +TITLE="LWASM" +HREF="c62.html"><LINK +REL="PREVIOUS" +TITLE="Macros" +HREF="x511.html"><LINK +REL="NEXT" +TITLE="Object Files and Sections" +HREF="x555.html"></HEAD +><BODY +CLASS="SECTION" +BGCOLOR="#FFFFFF" +TEXT="#000000" +LINK="#0000FF" +VLINK="#840084" +ALINK="#0000FF" +><DIV +CLASS="NAVHEADER" +><TABLE +SUMMARY="Header navigation table" +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TH +COLSPAN="3" +ALIGN="center" +>LW Tool Chain</TH +></TR +><TR +><TD +WIDTH="10%" +ALIGN="left" +VALIGN="bottom" +><A +HREF="x511.html" +ACCESSKEY="P" +>Prev</A +></TD +><TD +WIDTH="80%" +ALIGN="center" +VALIGN="bottom" +>Chapter 3. LWASM</TD +><TD +WIDTH="10%" +ALIGN="right" +VALIGN="bottom" +><A +HREF="x555.html" +ACCESSKEY="N" +>Next</A +></TD +></TR +></TABLE +><HR +ALIGN="LEFT" +WIDTH="100%"></DIV +><DIV +CLASS="SECTION" +><H1 +CLASS="SECTION" +><A +NAME="AEN534" +>3.8. Structures</A +></H1 +><P +> Structures are used to group related data in a fixed structure. A structure +consists a number of fields, defined in sequential order and which take up +specified size. The assembler does not enforce any means of access within a +structure; it assumes that whatever you are doing, you intended to do. +There are two pseudo ops that are used for defining structures. </P +><P +></P +><DIV +CLASS="VARIABLELIST" +><DL +><DT +><CODE +CLASS="PARAMETER" +>structname</CODE +> STRUCT</DT +><DD +><P +> This directive is used to begin the definition of a structure with name +<CODE +CLASS="PARAMETER" +>structname</CODE +>. Subsequent statements all form part of +the structure definition until the end of the structure is declared. </P +></DD +><DT +>ENDSTRUCT, ENDS</DT +><DD +><P +>This directive ends the definition of the structure. ENDSTRUCT is the +preferred form. Prior to version 3.0 of LWASM, ENDS was used to end a +section instead of a structure.</P +></DD +></DL +></DIV +><P +> Within a structure definition, only reservation pseudo ops are permitted. +Anything else will cause an assembly error.</P +><P +> Once a structure is defined, you can reserve an area of memory in the +same structure by using the structure name as the opcode. Structures can +also contain fields that are themselves structures. See the example +below.</P +><PRE +CLASS="PROGRAMLISTING" +>tstruct2 STRUCT +f1 rmb 1 +f2 rmb 1 + ENDSTRUCT + +tstruct STRUCT +field1 rmb 2 +field2 rmb 3 +field3 tstruct2 + ENDSTRUCT + + ORG $2000 +var1 tstruct +var2 tstruct2</PRE +><P +>Fields are referenced using a dot (.) as a separator. To refer to the +generic offset within a structure, use the structure name to the left of the +dot. If referring to a field within an actual variable, use the variable's +symbol name to the left of the dot.</P +><P +>You can also refer to the actual size of a structure (or a variable +declared as a structure) using the special symbol sizeof{structname} where +structname will be the name of the structure or the name of the +variable.</P +><P +>Essentially, structures are a shortcut for defining a vast number of +symbols. When a structure is defined, the assembler creates symbols for the +various fields in the form structname.fieldname as well as the appropriate +sizeof{structname} symbol. When a variable is declared as a structure, the +assembler does the same thing using the name of the variable. You will see +these symbols in the symbol table when the assembler is instructed to +provide a listing. For instance, the above listing will create the +following symbols (symbol values in parentheses): tstruct2.f1 (0), +tstruct2.f2 (1), sizeof{tstruct2} (2), tstruct.field1 (0), tstruct.field2 +(2), tstruct.field3 (5), tstruct.field3.f1 (5), tstruct.field3.f2 (6), +sizeof{tstruct.field3} (2), sizeof{tstruct} (7), var1 {$2000}, var1.field1 +{$2000}, var1.field2 {$2002}, var1.field3 {$2005}, var1.field3.f1 {$2005}, +var1.field3.f2 {$2006}, sizeof(var1.field3} (2), sizeof{var1} (7), var2 +($2007), var2.f1 ($2007), var2.f2 ($2008), sizeof{var2} (2). </P +></DIV +><DIV +CLASS="NAVFOOTER" +><HR +ALIGN="LEFT" +WIDTH="100%"><TABLE +SUMMARY="Footer navigation table" +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +><A +HREF="x511.html" +ACCESSKEY="P" +>Prev</A +></TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="index.html" +ACCESSKEY="H" +>Home</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +><A +HREF="x555.html" +ACCESSKEY="N" +>Next</A +></TD +></TR +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +>Macros</TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="c62.html" +ACCESSKEY="U" +>Up</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +>Object Files and Sections</TD +></TR +></TABLE +></DIV +></BODY +></HTML +> \ No newline at end of file